Artigo Fabiano
Artigo Fabiano
Artigo Fabiano
h i g h l i g h t s g r a p h i c a l a b s t r a c t
a r t i c l e i n f o a b s t r a c t
Article history: Several cement pastes with different amounts of metakaolin (MK) and/or limestone filler (LF) were pre-
Received 27 October 2016 pared. The water/cementitious materials ratio was maintained constant at 0.3, with addition of 0.5% wt/
Received in revised form 27 February 2017 wt of poly-carboxylate ether (PCE) superplasticizer admixture. The following parameters of the fresh
Accepted 1 March 2017
cement pastes were evaluated: the slump and spread, the Marsh funnel time, the plastic viscosity, yield
Available online 22 March 2017
stress, viscoelastic properties and thixotropy. After the curing of 7 day old pastes, compressive strength
tests were performed according to the Brazilian standard using 50 100 mm cylinder specimens. We
Keywords:
conclude that LF alone is not able to avoid segregation or bleeding, and there is no difference between
Rheology
Cement paste
cement pastes mixed with LF and pure OPC pastes, in terms of rheology. On the other hand, if one needs
Metakaolin low slump and low spread, the use of MK is recommended because this material creates a strong, thix-
Limestone filler otropic interconnected net inside of the paste, increasing the yield stress and the thixotropy of the
Mixture design cement paste. By adding 5–10% wt/wt MK, the average increase of compressive strength is approximately
45% at 7 days, compared to the control (only OPC, water and PCE). The maximum recommended amount
of LF or MK substitution in our case was 10% wt.
Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction especially in large-sized works or the ones that require the use of
special concretes, such as self-compacting concrete or high perfor-
The use of superplasticizer (SP) additives (also known as water mance concrete, among others [1,2]. Poly-carboxylate ether (PCE)
reducers) in civil construction has increased in recent years, is among the additives that has superior performance in terms of
viscosity reduction compared to common plasticizers, such as lig-
⇑ Corresponding author.
nosulfonates and naphthalenesulfonates [3]. On the other hand, if
poly-carboxylate ether is very effective in reducing cement paste
E-mail address: bombard@unifei.edu.br (A. José Faria Bombard).
http://dx.doi.org/10.1016/j.conbuildmat.2017.03.001
0950-0618/Ó 2017 Elsevier Ltd. All rights reserved.
F. Nazário Santos et al. / Construction and Building Materials 143 (2017) 92–103 93
viscosity, extra caution with additive overdose is a must. For but they did not employ Portland cement, neither any superplasti-
instance, a dose of 1 wt.% of water reducing admixture to the cizer [12]. Janotka et al., investigated in deep the rheology, com-
cement leads to cement particle segregation, with cement powder pressive strength, isothermal calorimetry and setting time of
settling very fast and causing phase separation with a layer con- mixtures of Portland cement with ‘‘metakaolin sands”, a type of
taining Portland cement (precipitate) at the bottom of the recipient SCM that was not pure metakaolin [13]. Their water/cement ratio
and a supernatant containing a lot of water and finer cement par- was 0.5, without addition of any water reducer plasticizer. They
ticles. Another negative effect of poly-carboxylate ether overdose is concluded: ‘‘. . .the presence of the metakaolin sands reduces the heat
the loss of thixotropy (and consequently the workability) of the released during the hydration process with respect to non-blended-
paste. cement pastes. The incorporation of metakaolin sand induces a
Siddique & Khan [4], describe that the use of supplementary decrease of the mechanical strength, with the decrease being higher
cementitious materials (SCM), such as blast furnace slag, fly ashes, as the metakaolin sand content increases even though they also pro-
microsilica, metakaolin, limestone filler, rice husk ashes, among duce a refinement in the pore structure and a decrease of the perme-
others, is increasingly growing. The use of such materials may be ability”. Sonebi et al. made an ‘‘Optimization of rheological
advantageous not only by the reduction of economic and environ- parameters and mechanical properties of superplasticized cement
mental costs of Portland cement manufacturing but also because it grouts containing metakaolin and viscosity modifying admixture”,
can greatly increase the final performance of structures, such as employing ‘‘Central composite experimental design (CCED)”, a sta-
compressive strength. In addition, some materials may help solv- tistical tool. They employed the same type of superplasticizer we
ing issues of segregation and workability loss caused by superplas- are studying, PCE. However, they stated: ‘‘The viscosity of cement
ticizers overdose. Martins & Bombard [5], showed that the use of grout was determined using a coaxial rotating cylinder viscometer
nanosilica in combination with adequate doses of poly- Fann (smooth cylinders, no serration).” Therefore, slippage could
carboxylate ether allows the acquisition of a relatively low appar- have occurred during their measurements [14]. Vance et al. pub-
ent (plastic) viscosity without workability loss (it maintains the lished a paper with the exact same materials that we are studying.
yield stress and thixotropy of the paste). Pera [6], reports that The title of their paper is: ‘‘The rheological properties of ternary
the first documented use of metakaolin in a large-scale work was binders containing Portland cement, limestone, and metakaolin
in the construction of the Jupiá Dam in 1962. Antoni et al. [7], or fly ash” [15]. However, different from us, they also did not
assessed the replacement of part of a Portland cement segment employ any water reducer admixture. Besides this, in their study,
with a combination of metakaolin and limestone filler, resulting the water-to-solid ratio (w/s) mass/mass were 0.40 and/or 0.45.
in ‘‘45% of substitution by 30% of metakaolin and 15% of limestone In our study, with the use of PCE SP, we prepared pastes with fixed
gives better mechanical properties than 100% OPC”. In addition to water/solids (w/s) ratio = 0.30. Favier et al., compared the rheolog-
that, they argue that ‘‘stoichiometric formation of monocarboalumi- ical properties of a geopolymer paste prepared mixing metakaolin
nate hydrate (MC). . . corresponds to an addition with a weight ratio with sodium silicate solution (water glass) versus cement paste.
of 2:1 metakaolin:limestone.” But the authors did not study the rhe- But not blends of OPC + MK [16]. More recently, Vance et al. com-
ology of mixtures. pared the rheology of suspensions (pastes) prepared with ‘‘inter-
A partial literature revision about rheological aspects of cement ground Portland limestone cements” ‘‘three blended limestone
pastes with supplementary cementitious materials follows. Cyr cements” They described a ratio w/s = 0.45 and again, without
et al. [8], investigated the shear thickening effect of superplasticiz- any superplasticizer [17]. Shahriar and Nehdi reported blends of
ers on the rheological behavior of cement pastes containing or not special cement (oil well API Class G OWC) mixed with four types
mineral additives. They compare the effect of: metakaolin (MK), of SCMs: MK, SF, (rice husk ashes) RHA, and low calcium FA, with
quartz (Qtz), fly ash (MFA) or silica fumes (SF). Their superplasti- replacement ranging from 5 to 15%. They also employed a poly-
cizers (SP) included five different types, but without any detail carboxylate-based high-range water reducing admixture, but with
about the chemistry of each SP. These authors studied three substi- water-to-binder mass ratio (w/b) of 0.44, which is the usual w/b
tution amounts of Portland cement by the four supplementary recommended for oil well cement formulations. In their study,
cementitious materials (SCM) above: 0% (only cement), 10% or they used Design of Experiments too. [18].
25%.They concluded that in terms of shear thickening effect ‘‘can For the reader interested in reviewing the significant literature
be amplified (metakaolin), unchanged (quartz, fly ashes) or on the rheology of cement pastes, as well as hundreds of scientific
reduced (silica fumes)”. Provis et al. [9], studied ‘‘the role of parti- papers published after 2001, the classical books by Tattersal [19]
cle shape” (morphology) of some SCM: ‘‘spherical particles of fly and Banfill [20] are advised.
ash”, ‘‘platy particles of metakaolin”, and the ‘‘angular particles of Metakaolin is a material with high pozzolanic activity. In addi-
blast furnace slag”, ‘‘both in the context of its effect on paste rhe- tion to being advantageous economically and environmentally, it
ology and on water demand”. The authors focused their report has the effect of improving mechanical resistance, as compressive
on particle shape effects in fresh pastes, particle packing and mix strength, since keeping low amount substitution of OPC by MK
design in geopolymer pastes and geopolymer concretes. However, (10%) by such way the hydration heat is similar to 100% OPC [21].
they did not mention any water reducer, plastifier or superplasti- Limestone filler addition to cement accelerates hydration of
fier. Banfill and Frias studied the rheology of blends cement with Portland clinker grains at early ages, improves the particle packing,
metakaolin or cement with paper sludge wastes, calcined at can increase the hydration rate from 1 day to 3 months and pro-
700 °C by 2 h [10]. The authors employed a sulfonated naphthalene duces the formation of calcium carbo-aluminates (hemicarboalu-
formaldehyde condensate as superplasticizer. They concluded that minate or monocarboaluminate), as a result of the reaction
‘‘the use of low concentrations of calcined paper sludge as a sup- between CaCO3 and C3A of Portland clinker or metakaolin (in case
plementary cementitious material. . . offers a route for utilising this of ternary blends) [22]. However, if partial substitution of OPC by
waste material, as an alternative to the. . . environmental burden LF can be advantageous (same reasons as MK: economic and envi-
associated with the production of metakaolin from natural kaolin- ronmental aspects), the formation of carbo-aluminates is a draw-
ite resources.” Moulin, et al. reported about the effects of ‘‘OPC back, in the case of a sulfate and chloride environment. [23].
blended with 30% (by weight of blend) calcined clay and its rheol- Around one hundred papers can be found reporting mixtures of
ogy. However, they also did not use any superplasticizer [11]. Pou- ‘‘limestone AND cement AND metakaolin”. However, very few
lesquen et al. studied the rheology of geopolymers prepared with [15,17,22,24–27], focus on the rheological properties of ternary
metakaolin, fumed silice and ‘‘Waterglass activating solutions”, blends of these three cementitious materials. Most of these works,
94 F. Nazário Santos et al. / Construction and Building Materials 143 (2017) 92–103
2.1. Materials
100
3410
80
1466
1572
T (%)
60
2881
1342,8
841,9
961
40
Fig. 3. Cumulative size distribution of Portland cement powder, metakaolin and limestone filler, measured by laser Dynamic Light Scattering, employing isopropyl alcohol as
carrier liquid.
of metakaolin and limestone consume calcium hydroxide, blends binary or ternary with OPC, MK and LF, with maximum
which may be completely absent in blends with high levels 20% replacement SCM.
of substitution at late ages. The metakaolin appears to react
faster in the system with limestone than in the binary meta- 2.3. Methods
kaolin/Portland cement blend. Also, the limestone reacts fas-
ter in the system with metakaolin than in the binary The flow time of each fresh paste was measured with the Marsh
limestone/Portland cement blend. These results point to funnel making it possible to measure the viscosity following the
strong synergistic effects with coupled substitutions of this ASTM D6910 [35,36]. Part of the paste was separated (400 ml)
type. Of course the consumption of calcium hydroxide could to perform the rheological measurements using stress-controlled
mean that the high substitution level blends may carbonate rheometer (Physica MCR-301, Anton Paar, Germany) equipped
more rapidly. This and other aspects of durability are cur- with the measuring system (a stirrer with two hollow vanes, model
rently being studied.” [7]. ST59-2V-44.3/120). The measuring rotor dimensions are: outer
diameter 59.00 mm, and length 44.3 mm. The cup of the rheometer
Therefore, based on these previous studies, we choose, with have inner diameter 70 mm, and a basket inset cage with serra-
help of Mixture Design of Experiments [28,29], to investigate tions inside which prevents wall slippage. Fig. 4 shows the stirrer.
96 F. Nazário Santos et al. / Construction and Building Materials 143 (2017) 92–103
70
LF
Compressive strength 7 days (MPa)
60 MK
50
40
30
20
10
0
0 5 10 15 20 25
SCM substitution (%)
Fig. 5. Compressive strength after 7 days for binary blends of Portland cement with
supplementary cementitious materials: OPC + MK or OPC + LF. Columns heights are
Fig. 4. Stirrer with two hollow vanes, model ST59-2V-44.3/120 (Anton Paar, the average value for 3 test specimens rupture. Error bars are the standard
Germany). deviation.
F. Nazário Santos et al. / Construction and Building Materials 143 (2017) 92–103 97
Table 3
Compressive strength after 7-day cure.
CP (%) MK (%) FC (%) R1 (MPa) R2 (MPa) R3 (MPa) Mean (MPa) Std Dev
100.000 0.0000 0.0000 33.14 30.79 50.40 38.11 10.71
96.667 1.6667 1.6667 61.00 49.00 54.00 54.67 6.03
95.000 5.0000 0.0000 56.27 51.00 59.00 55.42 4.07
95.000 0.0000 5.0000 36.53 53.87 44.91 45.10 8.67
93.333 3.3333 3.3333 40.60 40.65 40.45 40.57 0.10
91.667 6.6667 1.6667 40.75 40.75 40.47 40.66 0.16
91.667 1.6667 6.6667 54.92 42.83 27.63 41.79 13.67
90.000 10.0000 0.0000 56.00 50.00 48.00 51.33 4.16
90.000 0.0000 10.0000 51.38 40.90 43.00 45.09 5.54
90.000 5.0000 5.0000 56.00 46.00 61.00 54.33 7.64
93.333 3.3333 3.3333 41.44 42.30 40.00 41.25 1.16
93.333 3.3333 3.3333 43.76 42.43 41.00 42.40 1.38
93.333 3.3333 3.3333 38.00 40.57 41.00 39.86 1.62
93.333 3.3333 3.3333 41.95 39.76 39.02 40.24 1.54
96.667 1.6667 1.6667 38.44 38.66 42.53 39.88 2.30
80.000 20.0000 0.0000 39.28 44.09 35.00 39.46 4.55
80.000 0.0000 20.0000 48.17 43.53 40.35 44.02 3.93
80.000 10.0000 10.0000 47.00 46.89 46.00 46.63 0.55
86.667 6.6667 6.6667 45.00 43.00 33.00 40.33 6.43
90.000 0.0000 10.0000 52.00 50.99 39.00 47.33 7.23
90.000 10.0000 0.0000 58.41 53.44 57.84 56.56 2.72
3. Results and discussion 3.2. Slump, spreading and Marsh funnel time
3.1. Compressive strength after one week The spreading and the slump of each paste was measured in the
same test. Next, the time flow of each paste was measured using
As our focus was on the rheology of the fresh mixtures, com- the Marsh funnel. Table 4 summarizes the results for all tested
pressive strength was only measured with 7 days curing time. pastes. In some cases, it was not possible to measure all of these
Fig. 5 shows the results for binary blends. The results for all of 3 responses.
the mixtures are in Table 3. Fig. 6 shows the effect of the increase of metakaolin content as a
One can see in Fig. 5 that the maximum strength in our formu- function of the spreading (left axis) and the funnel time (right axis).
lations seems to be around 5% wt. substitution of Portland cement. The dotted line in Fig. 6 at 100 mm represents the spreading
Above 10% wt. MK, the strength start decreases. Besides, the paste threshold because this value is the internal diameter of modified
with 20% wt. substitution OPC by MK, was impossible to measure frustum. Therefore, spreadings smaller than 100 mm do not make
in the rheometer, because the maximum torque limit of the instru- sense in the test. The curves are only a guideline for the eyes. The
ment. In other words: the paste OPC:MK 80:20 was so plastic that paste with 10% of metakaolin (or more) does not flow inside the
its workability is bad. Even mixing this particular blend was diffi- Marsh funnel.
cult. Therefore, we focused the study on involving mixtures and sta-
tistical analysis in the range 0–10% wt. substitution OPC by SCM.
3.3. Yield stress measured by means of oscillatory amplitude sweep
The compressive strength of the pastes did not present great
changes compared to the control paste (only cement). However,
The yield stress can be experimentally measured in different
in the case that cement was replaced with 5% of metakaolin, the
ways. However, the result strongly depends on the measurement
compressive strength had a 45% average increase.
technique. One of them is the strain amplitude sweep test,
Table 4
Slump, spreading and Marsh funnel time for the tested pastes.
Portland cement (%) Metakaolin (%) Limestone filler (%) Slump (mm) Spreading (mm) Marsh Funnel (seconds)
*
100 0 0 602 31.41
* *
90 10 0 35
*
90 0 10 615 44.78
*
95 5 0 405 112.54
*
95 0 5 604 45.53
*
90 5 5 415 77.35
*
93.33 3.33 3.33 462 58.44
*
96.66 1.66 1.66 530 51.03
*
91.66 6.66 1.66 324 139.56
*
91.66 1.66 6.66 575 45.16
*
93.33 3.33 3.33 491 48.03
*
93.33 3.33 3.33 540 47.38
*
93.33 3.33 3.33 511 49.63
*
93.33 3.33 3.33 526 48.37
* *
80 20 0 11
*
80 0 20 538 71.76
* *
80 10 10 20
* *
86.66 6.66 6.66 50
*
96.66 1.66 1.66 562 42.88
*
Asterisk indicates that it was not possible to measure slump/spreading/time.
98 F. Nazário Santos et al. / Construction and Building Materials 143 (2017) 92–103
700 160
600 140
400 100
300 80
200 60
100 40
Spread >/= 100 mm
0 20
0 2 4 6 8 10
Metakaolin amount (%)
Fig. 6. Effect of metakaolin content on the spreading of the pastes (left axis) and on
the Marsh funnel time (right axis).
Table 5
Estimated regression coefficients for Yield VA (pseudo-components).
Table 6
Analysis of variance for yield VA (pseudo-components).
10
Fig. 9. Complex viscosity as a function of angular frequency for control pastes containing 3.3, 5, 6.7, and 10% metakaolin or limestone filler. This test was performed in
oscillatory mode at constant strain of 0.02%.
Fig. 9 shows that metakaolin contents above 3.3% lead to an All the values measured of viscoelastic moduli G0 and G00 , as well
increase of complex viscosity throughout entire analyzed fre- as the complex viscosity, are summarized in the Table 7.
quency range and that the pastes exhibited a pseudo plastic behav-
ior. On the other hand, the limestone filler did not cause any 3.5. Thixotropy of fresh pastes measured using ‘‘3 ITT” test
change in viscosity, except for the region above 100 rad/s, where
shear-thickening is observed. The shear-thickening behavior A three-interval of time test was used to obtain and evaluate
increased with filler content increase when no metakaolin was thixotropy (even if only for comparison) between the different
added. cement pastes formulations. According to MEZGER (2011), this test
100 F. Nazário Santos et al. / Construction and Building Materials 143 (2017) 92–103
Table 7
Elastic and viscous moduli (G0 e G00 ) and complex viscosity of pastes measured in frequency sweep tests.
Portland Cement (%) Metakaolin (%) Limestone filler (%) G’ (Pa) G” (Pa) g* (Pa.s)
100 0 0 36 7.3 7.3
90 10 0 790 83 158
90 0 10 47 8.8 9.5
95 5 0 67 8.3 13.6
95 0 5 33 5.8 6.6
90 5 5 68 8.2 13.7
93.33 3.33 3.33 64 8.0 12.8
96.66 1.66 1.66 42 6.6 8.5
91.66 6.66 1.66 122 13.6 24.6
91.66 1.66 6.66 38 6.4 7.6
93.33 3.33 3.33 35 5.5 7.0
93.33 3.33 3.33 29 5.6 6.0
93.33 3.33 3.33 38 6.2 7.7
93.33 3.33 3.33 37 6.8 7.5
* * *
80 20 0
80 0 20 40 6.0 8.0
80 10 10 1936 292 392
86.66 6.66 6.66 554 64.4 111.5
96.66 1.66 1.66 39 7.4 8.0
*
Asterisk indicates that was not possible to measure this paste in the rheometer, due torque limit.
second interval) is the same as the one used in the first interval.
In the third interval, the viscosity is monitored during a relatively
10 greater time and its values are recorded every 0.5 s to verify how
much of the initial viscosity is recovered and how much time does
it take for this recovery. In our case, the rotation profile and the
MK 6.6, LF 1.6% interval times used were as follows: 1st interval (0.1 rpm, 60 s,
1 MK 5%, LF 0
2nd interval 12 data points), 2nd interval (100 rpm, 50 s, 100 data points),
MK 5%, LF 5%
MK 3.3, LF 3.3% and 3rd interval (0.1 rpm, 250 s, 500 data points). Fig. 10 shows
MK 0, LF 10% some of the curves obtained in the 3-ITT thixotropy tests.
0,1 Fig. 10 shows that the pastes viscosity increases with metakao-
0 60 120 180 240 300 360 lin content. In addition, thixotropy (which is measured through
Time (s) recovery time (s) for a certain viscosity recovery level and/or vis-
cosity recovery degree (%) after 1 min) also strongly depends on
Fig. 10. Three-Interval thixotropy test. Viscosity as a function of time for 5 pastes
with different contents of metakaolin (MK) and limestone filler (LF).
100 160
MK
Thixotropic Recovery after 1 min (%)
is also called ‘‘3ITT” (three-interval of time test) [38]. In the first 90 LF 140
time interval of this thixotropy test, the sample is sheared under
Recovery time @ 63.2% (sec)
constant low rotation for 1 min to obtain the viscosity, which will 80 120
70 100
Table 8 Control: only
Thixotropy of cement-metakaolin-filler pastes Cement + water + SP
60 80
Paste Thixotropic recovery (%) Time (s) for 63.2% recovery
PC-MK-LF (%) after 1 min (1 1/e) of viscosity 50 60
91.6-6.7-1.7 66 47
95-5.0-0.0 55 105 40 40
90-5.0-5.0 57 82
93.4-3.3-3.3 (b) 52 99 30 MK 20
90-0.0-10 43 110 LF
90-10-0.0 90 14 20 0
96.6-1.7-1.7 45 126 0 5 10
91.6-1.7-6.7 38 158
95-0.0-5.0 48 99 Suppl. Cimentitious Mat. (%)
100-0.0-0.0 39 143
93.4-3.3-3.3 (a) 50 111 Fig. 11. Effect of metakaolin and limestone filler contents on the pastes thixotropy
93.4-3.3-3.3 (c) 49 123 measured on the 3rd interval after 1 min (left axis, black) and time for the viscosity
93.4-3.3-3.3 (d) 53 96 to return to 63.2% (1 1/e) of the reference value (right axis, red). (For interpre-
tation of the references to colour in this figure legend, the reader is referred to the
(a,b,c,d): replicate samples. web version of this article.)
F. Nazário Santos et al. / Construction and Building Materials 143 (2017) 92–103 101
Fig. 12. Mixture contour plot of thixotropic recovery (%) after 1 min. PC = Portland
Cement, MK = Metakaolin, LF = limestone filler. Fig. 13. Mixture contour plot (component amounts) for plastic viscosity measured
in rotational mode.
Table 9
Table 11
Estimated Regression coefficients for thixotropic recovery after 1 min (pseudo
Estimated regression coefficients for viscosity plastic (pseudo-components).
components).
Term Coef SE Coef T P VIF
Term Coef SE Coef T P VIF
PC 1.31 0.5312 * * 1.884
PC 39.38 5.316 * * 1.274
MK 11.18 0.5893 * * 2.319
MK 80.38 5.316 * * 1.274
LF 1.31 0.5312 * * 1.884
LF 40.38 5.316 * * 1.274
PC * MK 15.74 2.5925 6.07 0.000 2.628
S = 7.36259 PRESS = 1094.23
MK * LF 18.64 2.5925 7.19 0.000 2.628
R-Sq = 75.17% R-Sq(pred) R-Sq(adj)
S = 0.618696 PRESS = 38.2884
= 49.88% = 70.20%
R-Sq = 96.73% R-Sq(pred) = 63.66% R-Sq(adj) = 95.28%
Table 10
Analysis of variance for thixotropic recovery after 1 min (pseudo components). Table 12
Analysis of variance for viscosity plastic (pseudo-components).
Source DF Seq SS Adj SS Adj MS F P
Source DF Seq SS Adj SS Adj MS F P
Regression 2 1641.00 1641.00 820.500 15.14 0.001
Linear 2 1641.00 1641.00 820.500 15.14 0.001 Regression 4 101.925 101.9249 25.4812 66.57 0.000
Residual error 10 542.08 542.08 54.208 Linear 2 63.523 89.0158 44.5079 116.27 0.000
Lack-of-fit 7 532.08 532.08 76.011 22.80 0.013 Quadratic 2 38.402 38.4020 19.2010 50.16 0.000
Pure error 3 10.00 10.00 3.333 PC * MK 1 18.612 14.1184 14.1184 36.88 0.000
Total 12 2183.08 MK * LF 1 19.790 19.7904 19.7904 51.70 0.000
Residual error 9 3.445 3.4451 0.3828
Lack-of-fit 5 3.374 3.3741 0.6748 38.06 0.002
Pure error 4 0.071 0.0709 0.0177
Total 13 105.370
metakaolin content. Table 8 summarizes thixotropy results for the
tested pastes whenever measurement was possible.
Fig. 11 shows two ways of evaluating thixotropic results: per-
centage recovery of the viscosity after arbitrary time (we choose
1 min), and the time spent to recovery the same level of viscosity In the case of the regression model of thixotropic recovery, the
the 1st interval (commonly this level can be 63.2%). linear model was better than other, more complex models. The
One can see in Fig. 11 that the greater the added kaolin content, thixotropic recovery it is independent of the limestone filler Port-
the greater the thixotropy. On the other hand, this also leads to less land cement ratio and is a function only of the metakaolin content.
spreading and higher Marsh funnel time. Therefore, we concluded Tables 9 and 10 summarize the linear regression and ANOVA for
that metakaolin increases plasticity and thixotropy of cement thixotropic recovery after 1 min.
paste, i.e., it improves paste workability for metakaolin contents Fig. 13 shows the contour plot (in terms of component
of 5 to 8% but makes workability much more difficult for contents amounts) for plastic (or apparent) viscosity, measured in rotational
above 10%. mode in rheometer. The regression model here was quadratic,
Fig. 12 shows the contour plot for the percentage thixotropy because linear was insufficient to explain the viscosity results.
recovery level of the pastes after 1 min. The linear model is a good More complex models are not worth being employed, due to the
fit; and indicates how prevalent the effect of the metakaolin con- ‘‘lack-of-fit” changes. The quadratic model is the simplest with
tent over thixotropy is. acceptable R2 (adjust or predictable).
102 F. Nazário Santos et al. / Construction and Building Materials 143 (2017) 92–103
Fig. 15. Overlaid contour plot for yield stress and elastic modulus (oscillatory
rheometry); thixotropic recovery after 1 min and plastic viscosity (rotational
rheometry).
Fig. 14. Mixture contour plot (component amounts) for elastic modulus (G0 )
measured in oscillatory mode, in the rheometer. Fig. 14 clearly suggests that, if one is looking for pastes with an
elastic modulus of G0 > 120 Pa in these particular blends (PC + MK
+ LF, w/b = 0.30 and 0.5% wt. PCE), a minimum amount of 6% wt. of
Table 13 MK must be present in the formulations.
Estimated regression coefficients for elastic modulus (pseudo-components). However, let us see other responses in combination, since the
Term Coef SE Coef T P VIF ideal outcome would be a paste with plastic viscosity as low as
possible; fast thixotropic recovery; yield stress and elastic modulus
PC 30 15.51 * * 2.097
MK 787 17.06 * * 2.537 as high as possible. This is not an easy task. Fig. 13 shows an over-
LF 41 15.51 * * 2.097 laid plot of some of the responses. We arbitrarily chose: a)
PC * MK 1387 82.57 16.80 0.000 3.481 60 < G0 < 120 Pa; b) 2 < yield stress < 10 Pa; c) 2.5 < Plastic viscos-
MK * LF 1405 82.57 17.02 0.000 3.481 ity < 3.5 Pa.s and d) 60% < thixotropic recovery after 100 < 70%. Of
PC * MK * LF 1626 365.12 4.45 0.004 3.586
PC * MK * () 1139 277.87 4.10 0.006 1.625
course, in an ‘‘perfect world”, plastic viscosity should be less than
MK * LF * () 995 277.87 3.58 0.012 1.625 1 Pa.s, thixotropic recovery should approaches 100% as quick as
S = 17.1235 PRESS = 218,282 possible, and yield value or G’ should be as high as possible. The
R-Sq = 99.66% R-Sq(pred) = 57.66% R-Sq(adj) old problem of optimization of functions with maximums and min-
= 99.26%
imums. . . One solution, not ideal, but real and acceptable, is dis-
played in Fig. 15, as an overlaid contour plot.
The Fig. 15 suggests that a paste prepared with PC:MK:LF
90:5:5 must fulfill all the requirements, inside the white region
Table 14 delimited.
Analysis of variance for elastic modulus (pseudo-components).
The use of up to 5–10% metakaolin substitution may result in [16] A. Favier, J. Hot, G. Habert, N. Roussel, JBd’E de Lacaillerie, Flow properties of
MK-based geopolymer pastes. A comparative study with standard Portland
30–45% average increase in compressive strength after 7 days.
cement pastes, Soft Matter 10 (2014) 1134–1141.
A paste containing 90% Portland cement, blended with 5% Meta- [17] K. Vance, A. Arora, G. Sant, N. Neithalath, Rheological evaluations of
kaolin and 5% limestone filler, should present good thixotropy interground and blended cement-limestone suspensions, Constr. Build.
with 60% viscosity recovery after 1 min, elastic modulus above Mater. 79 (2015) 65–72.
[18] A. Shahriar, M.L. Nehdi, Optimization of rheological properties of oil well
60 Pa, and plastic viscosity 3.5 Pa.s The compressive strength cement slurries using experimental design, Mater. Struct. 45 (2012) 1403–
(7 days) of this blend was 54 ± 8 MPa. 1423.
[19] G.H. Tattersall, P.F.G. Banfill, The Rheology of Fresh Concrete, Pitman Books
Ltd, London, 1983.
[20] P.F.G. Banfill, Rheology of Fresh Cement and Concrete, Taylor & Francis, New
York, 1991.
Acknowledgements
[21] M. Frias, M.I.S. de Rojas, J. Cabrera, The effect that the pozzolanic reaction of
metakaolin has on the heat evolution in metakaolin-cement mortars, Cem.
The authors give special thanks to BASF SA for donating the Concr. Res. 30 (2000) 209–216.
chemical additives and to Metacaulim do Brasil Indústria e Comér- [22] L.M. Vizcaíno-Andrés, S. Sánchez-Berriel, S. Damas-Carrera, A. Pérez-
Hernández, K.L. Scrivener, J.F. Martirena-Hernández, Industrial trial to
cio Ltda (Jundiaí – SP, Brazil) for donating us MK. AJFB thanks the produce a low clinker, low carbon cement, Mater. Constr. 65 (317) (2015) 1–
financial support provided by CAPES and FAPEMIG (Grants: Rede 11.
Mineira de Química CEX-REDE-00010-14, PEP-00680-13, PEP- [23] V.L. Bonavetti, V.F. Rahhal, E.F. Irassar, Studies on the carboaluminate
formation in limestone filler-blended cements, Cem. Concr. Res. 31 (2001)
00231-15, ETC-00043-15, PEE-00081-16, PEP-00026-17 and APQ- 853–859.
01824-17). We are in debt to Professor Fábio H. Florenzano (USP [24] R. Bucher, P. Diederich, M. Mouret, G. Escadeillas, M. Cyr, Self-compacting
Lorena) by GPC analysis of PCE water reducer. Reading and com- concrete using flash-metakaolin: design method, Mater. Struct. 48 (2015)
1717–1737.
ments by Prof. Anderson P. Paiva, and Prof. Pedro P. Balestrassi as [25] I.P. Sfikas, E.G. Badogiannis, K.G. Trezos, Rheology and mechanical
well as the reviewer’s suggestions to improve the manuscript are characteristics of self-compacting concrete mixtures containing metakaolin,
deeply appreciated. Constr. Build. Mater. 64 (2014) 121–129.
[26] C. Perlot, P. Rougeau, S. Dehaudt, Slurry of metakaolin combined with
limestone addition for self-compacted concrete. Application for precast
References industry, Cem. Concr. Compos. 44 (2013) 50–57.
[27] A. Mohebbi, M. Shekarchi, M. Mahoutian, S. Mohebbi, Modeling the effects of
additives on rheological properties of fresh self-consolidating cement paste
[1] P.K. Mehta, P.J.M. Monteiro, Concrete – Microstructure, Properties And using artificial neural network, Comput. Concr. 8 (2011) 279–292.
Materials, third ed., McGraw Hill, New York, 2006.
[28] J. Cornell, Experiments with Mixtures, third ed., John Wiley & Sons, New York,
[2] R. Rixom, N. Mailvaganam, Chemical Admixtures For Concrete, third ed., E & Fn 2002.
Spon, London, 1999.
[29] R.E. Bruns, I.S. Scarminio, B. de Barros Neto, Data Handling in Science and
[3] A. Papo, L. Piani, Effect of various superplasticizers on the rheological Technology, Statistical Design – Chemometrics, vol. 25, Elsevier, Amsterdam,
properties of portland cement pastes, Cem. Concr. Res. 34 (2004) 2097–2101. 2006. ISBN: 978-0-444-52181-1.
[4] R. Siddique, M.I. Khan, Supplementary Cementing Materials, Springer-Verlag,
[30] M. Andersson, H. Ervanne, M.A. Glaus, S. Holgersson, P. Karttunen, H. Laine, B.
Berlin, 2011. Lothenbach, I. Puigdomenech, B. Schwyn, M. Snellman, H. Ueda, M. Vuorio, E.
[5] R.M. Martins, A.J.F. Bombard, Rheology of fresh cement paste with
Wieland, T. Yamamoto, Working Report 2008–28: ‘‘Development of
superplasticizer and nanosilica admixtures studied by response surface Methodology for Evaluation of Long-term Safety Aspects of Organic Cement
methodology, Mater. Struct. 45 (2012) 905–921. Paste Components”, POSIVA OY Working Report 2008–28, Eurajoki, Finland,
[6] J. Pera, Guest editorial – metakaolin and calcined clays, Cem. Concr. Compos. 2008, pp. 279.
23 (6) (2001) iii. [31] C.F. Ferraris, V.A. Hackley, A.I. Avilés, Measurement of Particle size distribution
[7] M. Antoni, J. Rossen, F. Martirena, K. Scrivener, Cement substitution by a
in portland cement powder: analysis of ASTM round robin studies, Cem. Concr.
combination of metakaolin and limestone, Cem. Concr. Res. 42 (2012) 1579– Aggregates 26 (2) (2004). Paper ID CCA11920.
1589. [32] API Recommended Practice 10B, 22nd ed., Recommended Practice for Testing
[8] M. Cyr, C. Legrand, M. Mouret, Study of the shear thickening effect of Well Cements, Appendix A, 1997, page 123.
superplasticizers on the rheological behaviour of cement pastes containing or [33] J. Ambroise, S. Maximilien, J. Pera, Properties of metakaolin blended cements,
not mineral additives, Cem. Concr. Res. 30 (2000) 1477–1483.
Adv. Cem. Based Mater. 1 (1994) 161–168.
[9] J.L. Provis, P. Duxson, J.S.J. van Deventer, The role of particle technology in [34] M.A. Helal, Effect of curing time on the physico-mechanical characteristics of
developing sustainable construction materials, Adv. Powder Technol. 21 (1)
the hardened cement pastes containing limestone, Cem. Concr. Res. 32 (2002)
(2010) 2–7. 447–450.
[10] P.F.G. Banfill, M. Frias, Rheology and conduction calorimetry of cement [35] ASTM D6910/D6910M-09: Standard Test Method for Marsh Funnel Viscosity
modified with calcined paper sludge, Cem. Concr. Res. 37 (2007) 184–190. of Clay Construction Slurries. ASTM International, West Conshohocken, PA
[11] E. Moulin, P. Blanc, D. Sorrentino, Influence of key cement chemical 19428–2959. United States.
parameters on the properties of metakaolin blended cements, Cement Concr.
[36] N. Roussel, R. le Roy, The Marsh cone: a test or a rheological apparatus?, Cem
Compos. 23 (2001) 463–469. Concr. Res. 35 (2005) 823–830.
[12] A. Poulesquen, F. Frizon, D. Lambertin, Rheological behavior of alkali-activated [37] ASTM C1749-12: Standard guide for measurement of the rheological
metakaolin during geopolymerization, J. Non-Cryst. Solids 357 (2011) 3565– properties of hydraulic cementitious paste using a rotational rheometer.
3571. ASTM International, West Conshohocken, PA 19428–2959. United States.
[13] I. Janotka, F. Puertas, M. Palacios, M. Kuliffayová, C. Varga, Metakaolin sand-
[38] T.G. Mezger, The Rheology Handbook, 3rd revised ed., Vincentz Network,
blended-cement pastes: rheology, hydration process and mechanical Hannover, 2011, pp. 72–74.
properties, Constr. Build. Mater. 24 (2010) 791–802.
[39] N. Roussel, P. Coussot, Fifty-cent rheometer for yield stress measurements:
[14] M. Sonebi, M. Lachemi, K.M.A. Hossain, Optimisation of rheological parameters from slump to spreading flow, J. Rheol. 49 (2005) 705–718.
and mechanical properties of superplasticised cement grouts containing [40] NBR 7215 – ‘‘Portland cement - Determination of compressive strength” (in
metakaolin and viscosity modifying admixture, Constr. Build. Mater. 38 portuguese), Associação Brasileira de Normas Técnicas, Rio de Janeiro, 1996.
(2013) 126–138. [41] ASTM C39/C39M 16b: Standard Test Method for Compressive Strength of
[15] K. Vance, A. Kumar, G. Sant, N. Neithalath, The rheological properties of ternary
Cylindrical Concrete Specimens. ASTM International, West Conshohocken, PA
binders containing Portland cement, limestone, and metakaolin or fly ash, 19428–2959. United States.
Cem. Concr. Res. 52 (2013) 196–207.